<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        * {
            padding: 0;
            margin: 0;
        }

        #box {
            width: 360px;
            height: 70px;
            padding-top: 360px;
            margin: 20px auto;
            border: 1px solid #cccccc;
            overflow: hidden;
            background: url("images/01big.jpg") no-repeat top center;
        }

        #box ul {
            list-style: none;
            border-top: 1px solid #cccccc;
            overflow: hidden;
        }

        #box li {
            float: left;
            cursor: pointer;
        }
    </style>
</head>

<script>
    window.onload = function () {
        var box = document.getElementById("box");
        var position = 1;
        var ids = ["li01","li02","li03","li04","li05"];

        function switchImage(idName,num) {
            var li = document.getElementById(idName);
            li.onmouseover = function () {
                if (position != num) {
                    box.style.backgroundImage = "url(images/0"+num+"big.jpg)";
                    position = num;
                }
            }
        }

        for (var i = 0; i < ids.length; i++) {
            switchImage(ids[i],(i+1));
        }

    }
</script>

<body>
<div id="box">
    <ul>
        <li id="li01"><img src="images/01.jpg" alt=""></li>
        <li id="li02"><img src="images/02.jpg" alt=""></li>
        <li id="li03"><img src="images/03.jpg" alt=""></li>
        <li id="li04"><img src="images/04.jpg" alt=""></li>
        <li id="li05"><img src="images/05.jpg" alt=""></li>
    </ul>
</div>
</body>
</html>